U.S. Pat. No. 8,328,423, for example, discloses a preload guide system for supporting from both side surfaces each of two journals for rotational driving of a large-sized rotation structure to restrict each of the journals to a predetermined position. The preload guide system disclosed in U.S. Pat. No. 8,328,423 includes two independent preload support systems. Each of the preload support systems connects bearings supporting the same surface of two journals with preloading, and adjusts preloading applied to the journals of the large-sized rotation structure. The providing of the two independent preload support systems enables return to a position determined originally even when mispositioning of the journal occurs in an axial direction due to factors such as thermal deformation induced by temperature change or weight of the large-sized rotation structure.